Re: what year is it?
If not already there, loosen the manual tilt/trim release valve 2 full turns (no more), then raise the engine to its full tilt position. Fill the reservoir to overflowing (the unit is delf bleeding). Tighten the release valve shut.
If the unit still does not operate, I'd suspect an air lock under the oil pump. To correct, apply 7 to 12 psi (pressurized air) to the reservoir. DO NOT over pressurize!
This should correct the air lock problem if it exists. Let us know what you find.